The set point theory describes the regulation of body weight. According to this theory, every human being has a certain body weight at which they feel relatively good and which is   kept constant by the metabolism under normal conditions. The level of this individual weight is called the set point. Its exact value is probably inherited and cannot be influenced significantly in the long term or in the long term without health problems occurring. This means that the body tries to maintain its normal starting weight – the set point.

weight levels off

It is possible to lose weight below the individual set point weight for a short time, but in the long term the weight will swing back towards the starting point. There is a counter-regulation that counteracts excessive weight loss. The same principle also applies in the opposite direction: following a high-calorie fattening diet, special changes occur in the metabolism, so that the previous, normal starting weight (set point) is reached again over a longer period of time.

The findings about the set point are not new. Scientific studies on the effects of weight loss or high-calorie nutrition on body weight and well-being were carried out as early as the 1950s and 1960s. Some of these studies are still considered classic today.

Studies in Set Point Theory

Probably the most important investigation was carried out in the USA in 1950 by the working group around Keys. The aim of the study was to examine the consequences of starvation on mental and physical well-being. Young, mentally healthy men of average weight took part in the study. The total duration of the study was one year.

During the first three months, the men ate normally, according to their previous eating habits. In the following six months, the actual diet phase, the individual amount of calories was halved. With this reduction in calories, the participants lost an average of 25 percent of their body weight. In the last three months of the study, the participants began to eat more and more and slowly gained weight again.

Even healthy people change their behavior

In addition to the change in weight, the results showed surprising deviations in the behavior of the men: During the diet phase, they were more and more preoccupied with food and could concentrate less and less on other things. This applied not only to topics of conversation, but also to reading material. Some began reading cookbooks and collecting recipes. They spent a lot of time worrying about upcoming meals. In some cases, the participants spent hours eating a meal that previously would have taken them only a few minutes.

They also experienced major mood swings. Most became irritable and nervous, many  depressed . They lost interest in social contacts and increasingly withdrew. The ability to concentrate and comprehension decreased significantly.

Lost sense of hunger

The same thing happened with physical performance. Many experienced  insomnia  or gastrointestinal problems. The basal metabolic rate and thus the energy consumption of the participants was reduced by around 40 percent. As a result, the men lost less weight than would have been expected based on the calorie restriction.

During the diet phase, the men had binge eating for the first time, which made those affected feel ashamed. The normal feeling of hunger, satiety and appetite was completely lost for most of them. These problems continued for a while after the diet was stopped. In the final phase of the study, the participants regained weight and regained their baseline weight.

What causes weight gain?

Another important study investigated the extent to which a person’s weight increases as a result of a sharp increase in the daily number of calories and what the consequences are for mental well-being. This investigation was carried out in 1968 by the American research group led by Sims. 15 men increased their weight by 25 percent within six months. At first, most of the participants gained a few kilograms without any problems.

However, this changed over time: Only four men gained significant weight due to overeating (maximum 10,000 calories per day). The remaining participants had to work extremely hard to gain more weight and eat large meals with a lot of effort in order to gain enough weight. Under the condition of a high-calorie diet, the basal metabolic rate of the participants increased significantly.

Baseline weight after overeating

This means that the metabolism used up more calories, for example by producing more heat and  sweat  . For this reason, the observed weight gain was limited and was less than would have been expected based on the calorie intake. Three participants had not achieved the goal of a 25 percent weight gain by the end of the study.

After stopping overeating, the majority of participants quickly regained weight and regained their baseline weight. Only two men remained overweight; these two had a family history of being  overweight  and gained weight rapidly and easily from the beginning of the study.

Conclusion: set point theory

The results confirm the set-point theory, according to which the individual body weight is largely determined biologically. Diets  are not a permanently effective method for weight regulation, since specific metabolic mechanisms counteract the diet and the set point is thus “defended”. This means that the weight is stabilized at the level of the starting weight.

Irregular eating,  fasting , vomiting, binge eating, and the use of laxatives or appetite suppressants all combine to significantly disrupt normal feelings of hunger and satiety. Therefore, even in previously healthy people (with normal eating habits) as part of a heavily reduced calorie diet, all the symptoms of  anorexia  or  binge eating can  occur.


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